PSA-based screening reduces deaths from prostate cancer, finds new review
A re-analysis of available evidence has found that Prostate-Specific Antigen (PSA)-based screening does reduce deaths from prostate cancer.
The findings, published today in the Annals of Internal Medicine, defies existing UK guidance which does not currently recommend universal screening.
The study concluded that ‘two important prostate cancer screening trials provide compatible evidence that screening reduces prostate cancer mortality’.
Current guidelines from the United States Preventive Services Task Force (USPSTF) recommend against PSA-based screening for prostate cancer because the evidence for the test showed very low probability that it would reduce the risk of dying, said the US-based researchers.
But they added that this recommendation relied heavily on results from the ERSPC (European Randomized Study of Screening for Prostate Cancer) and the PLCO (Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial), which offered conflicting results. The ERSPC showed a significant reduction and the PLCO showed no reduction.
The team of investigators from the University of Michigan and the National Cancer Institute sought to formally test whether the effects of screening on prostate cancer mortality differed between the ERSPC and PLCO and to estimate the effects of screening in both trials relative to no screening.
Using a mathematical model to account for differences in implementation compliance, and practice settings, they found no evidence that the effects of screening compared to no screening differed between ERSPC and PLCO and inferred that screening could ‘significantly reduce prostate cancer deaths’.
Although the findings suggest that current guidelines – recommending against routine PSA-based screening – may be revised, the researchers point out that questions remain about how to implement screening so that the benefits outweigh the potential harms of over-diagnosis and over-treatment.
In the UK, the NHS’s resistance to screening for prostate cancer is based on a recommendation made by the UK National Screening Committee.
The committee, which issued its latest recommendations on PSA screening in January last year, says that it does not currently recommend universal screening for prostate cancer.
The committee pointed out that evidence shows a benefit of prostate screening to reduce prostate cancer deaths by 21%. Despite this significant reduction, the harms of treating men who incorrectly test positive still outweigh the benefits, says the Committee.
It stressed that PSA is still a poor test for prostate cancer and a more specific and sensitive test is needed. PSA is also unable to distinguish between slow-growing and fast-growing cancers, said the committee.
Dr Andrew Green, GPC clinical and prescribing policy lead, told Pulse: ‘We already suspect that prostate cancer screening reduces prostate cancer deaths, but there is a world of difference between a difference in rate that is statistically significant for a population and a difference which is clinically significant for an individual. In any case, it should be all-cause mortality and not disease-specific mortality that is analysed.
‘However, the real question is not whether an occasional death can be prevented, but whether the costs to men’s physical and mental health caused by the inevitable over-diagnosis and over-treatment can be justified. The present evidence is that it cannot.’